Mr. Xie, the married head of a local sanitation bureau, and his much younger mistress exchanged what they assumed to be private messages on Sina Weibo (China’s popular microblogging equivalent to Twitter) arranging the details of a hotel rendevous and reimbursement for her shopping expenses. In fact, the conversations could be viewed by all 140 million Weibo users.

After several thousand Weibo users caught on, Mr. Xie finally realized his error and abruptly cancelled his account. His final message: “Sorry.” His young ladyfriend, on the other hand, has refused to close her account, saying it has sentimental value for her.